This invention relates to a process for removing condensates from light gaseous streams and in particular is applicable to gaseous streams which are subjected subsequently to analysis. The invention also relates to applications of this process and to apparatus for carrying out the process.
The light gaseous streams which are used, for example, in chemical, petroleum or petrochemical processes, such as gaseous streams composed principally of hydrogen and/or hydrocarbons having 1 to 6 carbon atoms, can be contaminated during these processes by condensates which often need to be removed. These condensates, whose exact chemical nature is not precisely known, are found particularly in the recycle gas of a catalytic hydro-reforming process. In particular, these condensates would comprise aromatic compounds and polyolefins.
These condensates are especially undesirable when analysing light gaseous currents, in which they can interfere with the determination of a gaseous compound. This is the case, for example, when analysing a gaseous current containing a small proportion of water, which has to be maintained close to a given value. Sometimes it is even absolutely necessary that the gas does not contain any water at all. This is particularly the case during the polymerisation of an alpha olefin in the presence of hydrogen using a catalyst containing organo-aluminum. Likewise it is sometimes desirable for the gas to contain a very small proportion of water. This is the case in certain catalytic processes in which optimum activity of the catalyst is obtained only in the presence of such a small proportion of water. This is so, in particular, in the processes for hydroreforming hydrocarbons.
In this instance, in order to check whether the proportion of water is in fact equal to the desired value, it is necessary to carry out a continuous analysis of the gaseous streams entering the hydroreforming unit. In the course of comparative analyses of such gaseous streams, the Applicants have established that continuous-analysis apparatus gives erroneous results after a certain period of operation; a situation which becomes even more serious when, in reliance on an erroneous result, an incorrect adjustment could be made to the proportion of water in the light gaseous stream and the activity of a catalyst, for example, could be seriously reduced. The Applicants have discovered that these erroneous results are caused by the presence of condensates in the gaseous streams, which are deposited on the measuring instruments.
It is particularly difficult to remove condensates contained in light gaseous streams, since the size of the condensate particles is often very small, in the order of one tenth of a micron, and these particles are not retained by conventional filters.